U.S. patent number 5,855,532 [Application Number 08/574,158] was granted by the patent office on 1999-01-05 for method and system for controlling automatic transmission.
This patent grant is currently assigned to Jatco Corporation. Invention is credited to Hideharu Sugiyama.
United States Patent |
5,855,532 |
Sugiyama |
January 5, 1999 |
Method and system for controlling automatic transmission
Abstract
An automatic transmission control system is capable of quickly
and accurately judging the normal state and faulty state of an
input shaft rotation speed sensor and/or an output shaft rotation
speed sensor. The system includes an input shaft rotation speed
sensor condition judging device for judging whether an input shaft
rotation speed sensor detecting a rotation speed NI of an input
shaft of the automatic transmission is in a normal or faulty state,
an output shaft rotation speed sensor condition judging device for
judging whether an output shaft rotation speed sensor detecting a
rotation speed No of an output shaft of the automatic transmission
is in a normal or faulty state, a multiplying means for multiplying
the rotation speed No of the output shaft with a current
transmission gear ratio, and comparing and judging means for
judging whether the multiplied value is coincident with the
rotation speed NI of the input shaft. On the basis of those
judgements, the output shaft rotation speed sensor is judged
whether it is in the normal state or not by the output shaft
rotation speed sensor condition judging device.
Inventors: |
Sugiyama; Hideharu (Fuji,
JP) |
Assignee: |
Jatco Corporation (Fuji,
JP)
|
Family
ID: |
18180787 |
Appl.
No.: |
08/574,158 |
Filed: |
December 18, 1995 |
Foreign Application Priority Data
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|
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Dec 27, 1994 [JP] |
|
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6-325804 |
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Current U.S.
Class: |
477/97; 477/906;
477/159 |
Current CPC
Class: |
F16H
61/12 (20130101); F16H 59/36 (20130101); F16H
2061/1232 (20130101); F16H 2061/1248 (20130101); Y10S
477/906 (20130101); F16H 2061/1208 (20130101); F16H
2061/1284 (20130101) |
Current International
Class: |
F16H
61/12 (20060101); F16H 59/36 (20060101); F16H
061/12 () |
Field of
Search: |
;477/906,97,154,159 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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0 575 094 |
|
Dec 1993 |
|
EP |
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34 47 626 |
|
Jul 1986 |
|
DE |
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42 31 821 |
|
Mar 1994 |
|
DE |
|
2-097765 |
|
Apr 1990 |
|
JP |
|
0 459 274 |
|
Dec 1991 |
|
JP |
|
Primary Examiner: Marmor; Charles A.
Assistant Examiner: Estremsky; Sherry Lynn
Attorney, Agent or Firm: Foley & Lardner
Claims
What is claimed is:
1. A method for controlling an automatic transmission comprising
the steps of:
judging whether an output shaft rotation speed sensor for detecting
a rotation speed of an output shaft of the automatic transmission
is in a normal state or a faulty state;
judging whether an input shaft rotation speed sensor for detecting
a rotation speed of an input shaft of the automatic transmission is
in a normal state or a faulty state;
multiplying the rotation speed of said output shaft detected by
said output shaft rotation speed sensor and a gear ratio of a
currently selected gear of the automatic transmission; and
comparing and judging whether a product value of the rotation speed
of said output shaft detected by said output shaft rotation speed
sensor and the gear ratio of the currently selected gear of the
automatic transmission matches with the rotation speed of the input
shaft;
wherein said step of judging a condition of said output shaft
rotation speed sensor judges that said output shaft rotation speed
sensor is in normal state on the basis of the judgement that the
product value of the rotation speed of said output shaft detected
by said output shaft rotation speed sensor and the currently
selected gear ratio of the automatic transmission matches with the
rotation speed of the input shaft as checked at the comparing and
judging step, and
wherein said step of judging whether said output shaft rotation
speed sensor is in normal state can be made only when the rotation
speed of the input shaft detected by said input shaft rotation
speed sensor falls within a predetermined range in said step of
judging the state of said output shaft rotation speed sensor.
2. A system for controlling an automatic transmission
comprising:
an output shaft rotation speed sensor condition judging device
judging whether an output shaft rotation speed sensor for detecting
a rotation speed of an output shaft of the automatic transmission
is in a normal or a faulty state;
an input shaft rotation speed sensor condition judging device
judging whether an input shaft rotation speed sensor for detecting
a rotation speed of an input shaft of the automatic transmission is
in a normal or a faulty state;
multiplying means for multiplying the rotation speed of said output
shaft detected by said output shaft rotation speed sensor and a
currently selected gear ratio of the automatic transmission;
and
comparing and judging means for comparing and judging whether a
product value of the rotation speed of said output shaft detected
by said output rotation speed sensor and the currently selected
gear ration of the automatic transmission matches with the rotation
speed of the input shaft;
wherein said output shaft rotation speed sensor condition judging
device judging a condition of said output shaft rotation speed
sensor judges that said output shaft rotation speed sensor is in
normal state on the basis of a judgment that the product value of
the rotation speed of said output shaft detected by said output
shaft rotation speed sensor and the gear ratio of the currently
selected gear of the automatic transmission equals the rotation
speed of the input shaft as checked by the comparing and judging
means, and
wherein the judgment that the output shaft rotation speed sensor is
in normal state can be made only when the rotation speed of the
input shaft detected by said input shaft rotation speed sensor
falls within a predetermined range in said step of judging a state
of said output shaft rotation speed sensor.
3. A method for controlling an automatic transmission comprising
the steps of:
judging whether an input shaft rotation speed sensor for detecting
a rotation speed of an input shaft of the automatic transmission is
in a normal state or a faulty state;
judging whether an output shaft rotation speed sensor for detecting
rotation speed of an output shaft of the automatic transmission is
in a normal state or a faulty state;
switching a control mode for the automatic transmission from a
normal mode, in which a transmission gear ratio is determined
depending upon predetermined shifting parameters, to a fail-safe
mode, in which a transmission gear ratio is fixed at a
predetermined transmission gear ratio, in response to detection of
a faulty state in at least one of said input shaft rotation speed
sensor and said output shaft rotation speed sensor;
checking whether a predetermined normal mode control resuming
condition is satisfied which includes at least establishing a power
train for transmitting a drive torque for a final drive, responsive
to termination of the faulty state of said at least one of said
input shaft rotation speed sensor and said output shaft rotation
speed sensor, while the control mode for the automatic transmission
is maintained in said fail-safe mode, and generating a normal mode
resuming demand when said predetermined normal mode control
resuming condition is satisfied; and
resuming the normal mode of control for said automatic transmission
in response to said normal mode resuming demand.
4. A method as claimed in claim 3, wherein said checking step is
performed by checking a position of a selector lever for detecting
the selector lever at other than neutral range position and park
range position for detecting establishment of said power train.
5. A method as claimed in claim 4, wherein
said step of judging a condition of said output shaft rotation
speed sensor judges that said output shaft rotation speed sensor is
in normal state on the basis of the judgement that the product
value of the rotation speed of said output shaft detected by said
output shaft rotation speed sensor and the gear ratio of the
currently selected gear of the automatic transmission matches with
the rotation speed of the input shaft.
6. A method as claimed in claim 4, wherein said step of judging a
condition of said input shaft rotation speed sensor judges that
said input shaft rotation speed sensor is in normal state on the
basis of the judgement that the product value of the output
rotation speed sensor and the gear ratio of the currently selected
gear of the automatic transmission matches with the rotation speed
of the input shaft.
7. A system for controlling an automatic transmission
comprising:
input shaft rotation sensor condition judging means for judging
whether an input shaft rotation speed sensor for detecting a
rotation speed of an input shaft of the automatic transmission is
in a normal state or a faulty state;
output shaft rotation speed sensor condition judging means for
judging whether an output shaft rotation speed sensor for detecting
rotation speed of an output shaft of the automatic transmission is
in a normal state or a faulty state;
control mode switching means for switching a control mode for the
automatic transmission from a normal mode, in which a transmission
gear ratio is determined depending upon predetermined shifting
parameters, to a fail-safe mode, in which a transmission gear ratio
is fixed at a predetermined transmission gear ratio, in response to
a detection of a faulty state in at least one of said input shaft
rotation speed sensor and said output shaft rotation speed sensor;
and
normal mode resuming condition detection means for checking whether
a predetermined normal mode control resuming condition is
satisfied, which includes at least establishing a power train for
transmitting a drive torque for a final drive responsive to
termination of the faulty state of said at least one of said input
shaft rotation speed sensor and said output shaft rotations speed
sensor, while the control mode for the automatic transmission is
maintained in said fail-safe mode, and generating a normal mode
resuming demand when said predetermined normal mode control
resuming condition is satisfied,
wherein said control mode switching means resumes the normal mode
of control for said automatic transmission in response to said
normal mode resuming demand.
8. A method for controlling an automatic transmission comprising
the steps of:
judging whether an output shaft rotation speed sensor for detecting
a rotation speed of an output shaft of the automatic transmission
is in a normal state or a faulty state;
judging whether an input shaft rotation speed sensor for detecting
a rotation speed of an input shaft of the automatic transmission is
in a normal state or a faulty state;
multiplying the rotation speed of said output shaft rotation speed
sensor and a gear ratio of a currently selected gear of the
automatic transmission; and
comparing and judging whether a product value of the rotation speed
of said output shaft detected by said output shaft rotation speed
sensor and the gear ratio of the currently selected gear of the
automatic transmission matches with the rotation speed of the input
shaft; and
wherein in said step of judging a condition of said input shaft
rotation speed sensor, an input shaft rotation speed sensor
condition judging device judges that said input shaft rotation
speed sensor is in a normal state on the basis that the product
value of the rotation speed of said output shaft detected by said
output shaft rotation speed sensor and the gear ratio of the
currently selected gear of the automatic transmission is equal to
the rotation speed of the input shaft as checked at the comparing
and judging step, and said step of judging the condition of said
input shaft rotation speed sensor judges that said input shaft
rotation speed sensor is in a faulty state when the rotation speed
of said input shaft rotation speed sensor is lower than a
predetermined input shaft rotation speed while a rotation speed of
an engine speed sensor is at least a predetermined engine rotation
speed and the rotation speed of the output shaft rotation speed
sensor is at least a predetermined output shaft rotation speed.
9. A system for controlling an automatic transmission
comprising:
input shaft rotation speed sensor condition judging means for
judging whether an input rotation shaft speed sensor for detecting
a rotation speed of an input shaft of the automatic transmission is
in a normal state or a faulty state;
output rotation speed sensor condition judging means for judging
whether an output shaft rotation speed sensor for detecting a
rotation speed of an output shaft of the automatic transmission is
in a normal state or a faulty state;
multiplying means for multiplying the rotation speed of said output
shaft detected by said output shaft rotation speed sensor and a
gear ratio of a currently selected gear of the automatic
transmission; and
comparing and judging means for comparing and judging whether a
product value of the rotation speed of said output shaft detected
by said output shaft rotation speed sensor and the gear ratio of
the currently selected gear of the automatic transmission matches
with the rotation speed of the input shaft;
wherein said input shaft rotation speed sensor condition judging
means judging a condition of said input shaft rotation speed sensor
judges that said input shaft rotation speed sensor is in normal
state on the basis of judgment that the product value of the
rotation speed of said output shaft detected by said output shaft
rotation speed sensor and the gear ratio of the currently selected
gear of the automatic transmission is equal to the rotation speed
of the input shaft as checked by the comparing and judging means,
and judges that said input shaft rotation speed sensor is in a
faulty state when the rotation speed of said input shaft rotation
speed sensor is lower than a predetermined input shaft rotation
speed while a rotation speed of an engine speed sensor is at least
a predetermined engine rotation speed and the rotation speed of
said output shaft rotation speed sensor is at least a predetermined
output shaft rotation speed.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control method for an automatic
transmission and a system therefor, which can judge whether a
rotation speed sensor for detecting rotation speed of an input
shaft and an output shaft of an automatic transmission is in normal
condition or abnormal condition.
2. Description of the Related Art
In an automatic transmission, it is required to progressibly vary
supply pressure for frictional engaging element newly engaging upon
shifting operation. At the same time, an output torque of an engine
is temporarily lowered for reducing variation of torque which can
be caused upon shifting operation and thus achieving smooth
shifting operation without causing shift shock. Therefore, there is
generally employed a method for appropriately adjusting a supply
pressure for frictional engaging element by means of a line
pressure controlling valve or so forth, on the basis of detection
signals detected by employing an input shaft rotation speed sensor
detecting rotation speed of an input shaft of the automatic
transmission and an output shaft rotation speed sensor detecting
rotation speed of an output shaft of the automatic
transmission.
However, when failure is caused on the input shaft rotation speed
sensor or the output shaft rotation speed sensor, it becomes
impossible to perform appropriate control for reducing shift shock
as set forth above. Therefore, in the prior art, when failure is
caused in the input shaft rotation speed sensor or the output shaft
rotation speed sensor, an appropriate gear ratio is set or a supply
pressure for the frictional engaging element is set in order to
avoid problem in a control system. Such fail-safe control system
for the automatic transmission has been proposed in Japanese Patent
Application Laid-open No. 97765/1990.
A fail detection system for an automatic transmission as disclosed
in Japanese Patent Application Laid-open No. 97765/1990 may detect
any failure caused on the input shaft rotation speed sensor or the
output shaft rotation speed sensor.
However, in such conventional systems, it is not possible to
identify which of the input shaft rotation speed sensor or the
output shaft rotation speed sensor is the faulty sensor. Therefore,
it becomes difficult to optimally perform the fail-safe process.
Therefore, the fail-safe process is inherently performed under
assumption that all sensors are in faulty condition. For instance,
despite of the fact that failure is caused only in the input shaft
rotation speed sensor, a gear ratio of the automatic transmission
is held at third speed ratio, in which the input shaft and the
output shaft of the transmission are directly coupled for rotation
at equal speeds, and the supply pressure (line pressure) to be
supplied to the frictional engaging element which becomes engaged
upon shifting is adjusted to the maximum value. Therefore, it
inherently cause degradation of riding quality, and an
unnecessarily long period is required for restoration from this
condition.
On the other hand, since the faulty rotation speed sensor cannot be
identified, it is also difficult to store the individual fault
history of the rotation speed sensor.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a control
method for an automatic transmission which can quickly and
correctly identify normal conditions and abnormal conditions of an
input shaft rotation speed sensor and an output shaft rotation
speed sensor, and a system therefor.
Another object of the invention is to provide a control method for
an automatic transmission which can quickly restore from fail-safe
process when judgement is made that the input shaft rotation speed
sensor and the output shaft rotation speed sensor are normal.
According to the first aspect of the invention, a method for
controlling an automatic transmission comprises the steps of:
judging whether an input shaft rotation speed sensor for detecting
rotation speed of an input shaft of the automatic transmission is
in normal state or faulty state;
judging whether an output shaft rotation speed sensor for detecting
rotation speed of an output shaft of the automatic transmission is
in normal state or faulty state;
multiplying the rotation speed of the output shaft detected by the
output shaft rotation speed sensor and a currently selected gear
ratio of the automatic transmission;
comparing and judging whether a product value of the rotation speed
of the output shaft detected by the output shaft rotation speed
sensor and the currently selected gear ratio of the automatic
transmission matches with the rotation speed of the input shaft,
and
the step of judging for the condition of the output shaft rotation
speed sensor judging that the output shaft rotation speed sensor is
in normal state on the basis of the judgement that the product
value of the rotation speed of the output shaft detected by the
output shaft rotation speed sensor and the currently selected gear
ratio of the automatic transmission matches with the rotation speed
of the input shaft, as checked at the comparing and judging
step.
Here, the judgement that the output shaft rotation speed sensor is
in normal state is made only when the rotation speed of the input
shaft detected by the input shaft rotation speed sensor falls
within a predetermined range, in the step of judging the state of
the output shaft rotation speed sensor.
According to the second aspect of the invention, a method for
controlling an automatic transmission comprises the steps of:
judging whether an input shaft rotation speed sensor for detecting
rotation speed of an input shaft of the automatic transmission is
in normal state or faulty state;
judging whether an output shaft rotation speed sensor for detecting
rotation speed of an output shaft of the automatic transmission is
in normal state or faulty state;
multiplying the rotation speed of the output shaft detected by the
output shaft rotation speed sensor and a currently selected gear
ratio of the automatic transmission;
comparing and judging whether a product value of the rotation speed
of the output shaft detected by the output shaft rotation speed
sensor and the currently selected gear ratio of the automatic
transmission matches with the rotation speed of the input shaft,
and
the step of judging for the condition of the input shaft rotation
speed sensor judging that the output shaft rotation speed sensor is
in normal state on the basis of the judgement that the product
value of the rotation speed of the output shaft detected by the
output shaft rotation speed sensor and the currently selected gear
ratio of the automatic transmission matches with the rotation speed
of the input shaft as checked at the comparing and judging
step.
According to the third aspect of the invention, a system for
controlling an automatic transmission comprising:
an input shaft rotation speed sensor condition judging device
judging whether an input shaft rotation speed sensor for detecting
rotation speed of an input shaft of the automatic transmission is
in normal state or faulty state;
an output shaft rotation speed sensor condition judging device
judging whether an output shaft rotation speed sensor for detecting
rotation speed of an output shaft of the automatic transmission is
in normal state or faulty state;
multiplying means for multiplying the rotation speed of the output
shaft detected by the output shaft rotation speed sensor and a
currently selected gear ratio of the automatic transmission;
comparing and judging means for comparing and judging whether a
product value of the rotation speed of the output shaft detected by
the output shaft rotation speed sensor and the currently selected
gear ratio of the automatic transmission matches with the rotation
speed of the input shaft, and
the output shaft rotation speed sensor condition judging device
judging for the condition of the output shaft rotation speed sensor
judging that the output shaft rotation speed sensor is in normal
state on the basis of the judgement that the product value of the
rotation speed of the output shaft detected by the output shaft
rotation speed sensor and the currently selected gear ratio of the
automatic transmission matches with the rotation speed of the input
shaft as checked by the comparing and judging means.
It is preferred that the judgement that the output shaft rotation
speed sensor is in normal state occur only when the rotation speed
of the input shaft detected by the input shaft rotation speed
sensor falls within a predetermined range, in the step of making
judgement of the state of the output shaft rotation speed
sensor.
According to the fourth aspect of the invention, a system for
controlling an automatic transmission comprises:
input shaft rotation speed sensor condition judging means for
judging whether an input shaft rotation speed sensor for detecting
rotation speed of an input shaft of the automatic transmission is
in normal state or faulty state;
output shaft rotation speed sensor condition judging means for
judging whether an output shaft rotation speed sensor for detecting
rotation speed of an output shaft of the automatic transmission is
in normal state or faulty state;
multiplying means for multiplying the rotation speed of the output
shaft detected by the output shaft rotation speed sensor and a
currently selected gear ratio of the automatic transmission;
comparing and judging means for comparing and judging whether a
product value of the rotation gear of the output shaft detected by
the output shaft rotation speed sensor and the currently selected
gear ratio of the automatic transmission matches with the rotation
speed of the input shaft, and
the input shaft rotation speed sensor condition judging means
judging for the condition of the input shaft rotation speed sensor
judging that the output shaft rotation speed sensor is in normal
state on the basis of the judgement that the product value of the
rotation speed of the output shaft detected by the output shaft
rotation speed sensor and the currently selected gear ratio of the
automatic transmission matches with the rotation speed of the input
shaft as checked by the comparing and judging means.
According to the fifth aspect of the invention, a method for
controlling an automatic transmission comprises the steps of:
judging whether an input shaft rotation speed sensor for detecting
rotation speed of an input shaft of the automatic transmission is
in normal state or faulty state;
judging whether an output shaft rotation speed sensor for detecting
rotation speed of an output shaft of the automatic transmission is
in normal state or faulty state;
switching a control mode for the automatic transmission from a
normal mode, in which a transmission gear ratio is determined
depending upon predetermined shifting parameters, to a fail-safe
mode, in which a transmission gear ratio is fixed at a
predetermined transmission gear ratio, in response to detection of
faulty state in at least one of the input shaft rotation speed
sensor and the output shaft rotation speed sensor;
checking whether a predetermined normal mode control resuming
condition which includes at least establishment of power train for
transmitting a drive torque for a final drive, responsive to
termination of faulty state of the at least one of the input shaft
rotation speed sensor and the output shaft rotation speed sensor,
while the control mode for the automatic transmission is maintained
in the fail-safe mode, and generating a normal mode resuming demand
when the predetermined normal mode control resuming condition is
satisfied;
resuming the normal mode of control for the automatic transmission
in response to the normal mode resuming demand.
According to the sixth aspect of the invention, a system for
controlling an automatic transmission comprises:
input shaft rotation sensor condition judging means for judging
whether an input shaft rotation speed sensor for detecting rotation
speed of an input shaft of the automatic transmission is in normal
state or faulty state;
output shaft rotation sensor condition judging means for judging
whether an output shaft rotation speed sensor for detecting
rotation speed of an output shaft of the automatic transmission is
in normal state or faulty state;
control mode switching means for switching a control mode for the
automatic transmission from a normal mode, in which a transmission
gear ratio is determined depending upon predetermined shifting
parameters, to a fail-safe mode, in which a transmission gear ratio
is fixed at a predetermined transmission gear ratio, in response to
detection of faulty state in at least one of the input shaft
rotation speed sensor and the output shaft rotation speed
sensor;
normal mode resuming condition detecting means for checking whether
a predetermined normal mode control resuming condition which
includes at least establishment of power train for transmitting a
drive torque for a final drive, responsive to termination of faulty
state of the at least one of the input shaft rotation speed sensor
and the output shaft rotation speed sensor, while the control mode
for the automatic transmission is maintained in the fail-safe mode,
and generating a normal mode resuming demand when the predetermined
normal mode control resuming condition is satisfied; and
the control mode switching means resuming the normal mode of
control for the automatic transmission in response to the normal
mode resuming demand.
With the present invention, the input shaft rotation speed sensor
detects rotation speed of the input shaft of the automatic
transmission, and, on the other hand, the output shaft rotation
speed sensor detects rotation speed of the output shaft of the
automatic transmission. These detection signals are output to the
input shaft rotation speed sensor condition judging device and the
output shaft rotation speed condition judging device.
Then, the output shaft rotation speed sensor condition judging
device performs a judgement of the normality of the output shaft
rotation speed sensor on the basis of the judgement of the
comparing and judging means that the multiplied value of the
rotation speed of the output shaft and the gear ratio of the
automatic transmission and the rotation speed of the input
shaft.
On the other hand, the input shaft rotation speed sensor detects
rotation speed of the input shaft of the automatic transmission,
and, on the other hand, the output shaft rotation speed sensor
detects rotation speed of the output shaft of the automatic
transmission. These detection signals are output to the input shaft
rotation speed sensor condition judging device and the output shaft
rotation speed condition judging device.
The input shaft rotation speed sensor condition judging device
performs a judgement of the normality of the input shaft rotation
speed sensor on the basis of the judgement of the comparing and
judging means that the multiplied value of the rotation speed of
the output shaft and the gear ratio of the automatic transmission
and the rotation speed of the input shaft.
As set forth, since the output shaft rotation speed sensor
condition judging device which judges whether the output shaft
rotation speed sensor is in the normal condition or faulty
condition, is provided, it becomes possible to discriminate whether
the output shaft rotation speed sensor is in the abnormal
condition. Therefore, an appropriate fail-safe process can be
performed. In addition, a history of normal condition and abnormal
condition can be maintained. In addition, restoring the normal
control process from the fail-safe process can be done quickly and
accurately, upon a judgement of normality of the output shaft
rotation speed sensor.
On the other hand, since the input shaft rotation speed sensor
condition judging device which makes judgement whether the input
shaft rotation speed sensor is in the normal condition or faulty
condition, is provided, it becomes possible to discriminate whether
the input shaft rotation speed sensor is in the abnormal condition.
Therefore, an appropriate fail-safe process can be performed. In
addition, a history of normal condition and abnormal condition can
be maintained. In addition, restoring the normal control process
from the fail-safe process can be done quickly and accurately, upon
a judgement of normality of the output shaft rotation speed
sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be understood more fully from the
detailed description given herebelow and from the accompanying
drawings of the preferred embodiment of the invention, which,
however, should not be taken to be limitative to the present
invention, but are for explanation and understanding only.
In the drawings:
FIG. 1 is a block diagram showing a general construction of one
embodiment of a control method for an automatic transmission and a
system therefor, applied for a forward four speed automatic
transmission with an over-drive function; and
FIG. 2 is a flowchart showing a flow of the operation of the
embodiment of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
One embodiment, in which a system realizing a control method for an
automatic transmission is applied for a forward four speed
automatic transmission with an over-drive function, will be
discussed hereinafter in detail with reference to the accompanying
drawings. In the following description, numerous specific details
are set forth in order to provide a thorough understanding of the
present invention. It will be obvious, however, to those skilled in
the art that the present invention may be practiced without these
specific details. In other instances, well-known structures are not
shown in detail in order to unnecessarily obscure the present
invention.
FIG. 1 shows a concept of the control method for an automatic
transmission and a system therefor, and FIG. 2 shows a flow of the
process.
On a crankshaft 12 of an engine 11, an input shaft 15 of an
automatic transmission 14 is connected via a torque converter 13.
For an output shaft 16 of the automatic transmission, drive wheels
are connected via a not shown differential gear unit.
Information relating to a rotation speed NE of a crankshaft 12
detected by an engine speed sensor 17 is adapted to be output to an
input shaft rotation speed sensor condition judging device 18. To
the input shaft rotation speed sensor condition judging device 18,
in addition to information relating to a rotation speed NI of an
input shaft 15 of an automatic transmission 14 detected by an input
shaft rotation speed sensor 19, information relating to a rotation
speed NO of an output shaft 16 of the automatic transmission 14
detected by an output shaft rotation speed sensor 20.
The information representative of rotation speed NI of the input
shaft 15 of the automatic transmission 14 from the input shaft
rotation speed sensor 19 is also output to an output shaft rotation
sensor condition judging device 21 and a comparing and judging
means 22.
The information relating to the rotation speed NO of the output
shaft 16 of the automatic transmission 14 from the output shaft
rotation speed sensor 20 is output to a multiplying means 23 and a
deceleration calculating means 24. The multiplying means 23
multiplies a gear ratio G of the automatic transmission 14 and the
rotation speed NO of the output shaft 16. The product thus derived
by the multiplying means 23 is output to the comparing and judging
means 22. The comparing and judging means 22 judges whether a
product of the current gear ratio G of the automatic transmission
14 and the rotation speed NO of the output shaft 16 and the
rotation speed NI of the input shaft 15 are matched or not. The
result of that judgement is output to the input shaft rotation
speed sensor condition judging device 18 and the output shaft
rotation sensor condition judging device 21, respectively. On the
other hand, the comparing judging means 22 calculates a variation
rate of the rotation speed NO of the output shaft 16 and outputs to
the output shaft rotation sensor condition judging device 21.
It should be noted that to the input shaft rotation speed sensor
condition judgement device 18 and the output shaft rotation sensor
condition judgement device 21, information from an inhibitor switch
25 detecting the position of a not shown selector lever of the
automatic transmission 14 is also input.
The input shaft rotation speed sensor condition judging device 18
judges the failure of the input shaft rotation speed sensor 19 when
the rotation speed NI of the input shaft 15 input by the input
shaft rotation speed sensor 19 is lower than or equal to a
predetermined value (e.g. lower than or equal to 600 r.p.m.)
despite the fact that a rotation speed NE of the crankshaft 12
detected by the engine speed sensor 17 is higher than or equal to a
predetermined value (e.g. 1500 r.p.m.) and the rotation speed NO of
the output shaft 16 detected by the output shaft rotation speed
sensor 20 is higher than or equal to a predetermined value (e.g.
2000 r.p.m.). Then, fault information is output to an input shaft
rotation speed sensor fail-safe processing device 26.
The input shaft rotation speed sensor fail-safe processing device
26 initiates a fail-safe process of the input shaft rotation speed
sensor 19 on the basis of fault information from the input shaft
rotation speed sensor condition judging device 18. The input shaft
rotation speed sensor fail-safe processing device 26 terminates the
fail-safe process for the input shaft rotation speed sensor 19 on
the basis of a fail restoring information (which will be discussed
later) from the input shaft rotation speed sensor condition judging
device 18. In the shown embodiment, the fail-safe process of the
input shaft rotation speed sensor 19 is performed to fix a supply
pressure (line pressure) of a line pressure controlling valve 27
incorporated in a not shown hydraulic control circuit of the
automatic transmission 14 for adjusting the supply pressure for not
shown frictional engaging elements of the automatic transmission 14
for switching engaging condition upon shifting. In conjunction
therewith, the fail-safe process stops actuation of the output
torque lowering device 28 for temporarily lowering the output
torque of the crankshaft 12 of the engine, upon shifting.
On the other hand, the output shaft rotation sensor condition
judging device 21 judges the of failure of the output shaft
rotation speed sensor 20 when the variation rate of the rotation
speed NO of the output shaft 16 derived by the deceleration
calculating means 24, namely deceleration of the vehicle is greater
than or equal to predetermined value B which is not possibly caused
in the actual vehicle. The fault information is then output to an
output shaft rotation speed sensor fail-safe processing device
29.
The output shaft rotation speed sensor fail-safe processing device
29 initiates a fail-safe process for the output shaft rotation
speed sensor 20 on the basis of fault information from the output
shaft rotation sensor condition judging device 21. Then, the output
shaft rotation speed sensor fail-safe processing device 29
terminates the fail-safe process on the basis of a fail restoring
information (which will be discussed later) from the output shaft
rotation sensor condition judging device 21. In the shown
embodiment, the fail-safe process for the output shaft rotation
speed sensor 20 is to hold the gear ratio of the automatic
transmission 14 at the third speed ratio by operating a shift
solenoid incorporated in the not shown hydraulic control
system.
It should be noted that when the output shaft rotation speed sensor
20 or the input shaft rotation speed sensor 19 resumes the normal
state, or when a faulty sensor is replaced with a new one, it
becomes necessary to terminate the fail-safe process. In this case,
in the shown embodiment, when the not shown selector position
information from the inhibitor switch 25 is P (parking) range or N
(neutral) range, it is not possible to determine whether the input
shaft rotation speed sensor 19 and the output shaft rotation speed
sensor 20 are in normal condition or in faulty condition by the
input shaft rotation speed sensor condition judging device 18 and
the output shaft rotation sensor condition judging device 21.
Therefore, at this condition, the fail-safe process for the input
shaft rotation speed sensor 19 and the output shaft rotation speed
sensor 20 will not be terminated.
On the other hand, when the rotation speed NI of the input shaft 15
as detected by the input shaft rotation speed sensor 19 is out of a
predetermined range (e.g. 1100 r.p.m. to 1300 r.p.m. where
possibility that the third speed ratio is selected, is high),
termination of the fail-safe process for the input shaft rotation
speed sensor 19 or the output shaft rotation speed sensor 20 should
cause shifting operation other than the third speed ratio
irrespective of the intention of the driver. Therefore, in such
case, the input shaft rotation speed sensor condition judging
device 18 and the output shaft rotation sensor condition judging
device 21 will not output the information for terminating the
fail-safe process for the input shaft rotation speed sensor 19 and
the output shaft rotation speed sensor 20 to the input shaft
rotation speed sensor fail-safe processing device 26 and the output
shaft rotation speed sensor fail-safe processing device 29. In view
of this, it is effective to certainly avoid a problem to cause
shifting from the third speed ratio selected during fail-safe
process to other gear ratio upon termination of the fail-safe
process for the input shaft rotation speed sensor 19 and the output
shaft rotation speed sensor 20 by combining a condition of an open
angle of a not shown throttle valve with the condition of the
rotation speed NI of the input shaft 15.
Furthermore, when the rotation speed NI of the input shaft rotation
speed sensor 19 does not match with the product of the rotation
speed NO and the current gear ratio G, it is possible that the
vehicle is in shifting transition by manual shifting or that some
failure is caused. Therefore, in such case, the fail-safe processes
for the input shaft rotation speed sensor 19 and the output shaft
rotation speed sensor 20 are not terminated.
As shown in the flow of the process in FIG. 2, the output shaft
rotation sensor condition judging device 21 judges whether the
detection signal from the output shaft rotation speed sensor 20 is
normal at a step S1. Then, if the detection signal from the output
shaft rotation speed sensor 20 is not normal as checked at the step
S1, the output shaft rotation speed sensor fail-safe processing
device 29 initiates the fail-safe process on the basis of fault
information of the output shaft rotation speed sensor 20, at a step
S2.
On the other hand, when the output shaft rotation sensor condition
judging device 21 judges that the detection signal from the output
shaft rotation speed sensor 20 as checked at the step S1 is normal,
the process is advanced to a step S3 to check whether the detection
signal from the input shaft rotation speed sensor 19 is normal by
the input shaft rotation speed sensor condition judging device 18.
If a judgement is made that the detection signal from the input
shaft rotation speed sensor 19 is not normal as checked at the step
S3 by the input shaft rotation speed sensor condition judging
device 18, the output shaft rotation speed sensor fail-safe
processing device 29 initiates the fail-safe operation on the basis
of the fault information of the input shaft rotation speed sensor
19.
When the input shaft rotation speed sensor condition judging device
18 judges that the detection signal from the input shaft rotation
speed sensor condition judging device 18 is normal at the step S3,
the process is advanced to a step S5 to check whether the selected
position of the selector lever is in P range or N range. When the
input shaft rotation speed sensor condition judging device 18 and
the output shaft rotation sensor condition judgement device 21
judge that the select position of the selector lever is P range or
N range, the process directly goes END. On the other hand, when a
judgement is made that the select position of the selector lever is
not P range or N range by the input shaft rotation speed sensor
condition judging device 18 and the output shaft rotation sensor
condition judging device 21 at the step S5, the process is advanced
to a step S6 to perform checking whether the rotation speed NI of
the input shaft 15 is within the predetermined range.
When the rotation speed NI of the input shaft 15 as checked at the
step S6 is out of the predetermined range, the process directly
goes END. On the other hand, when the rotation speed NI of the
input shaft 15 is within the predetermined range, the process is
advanced to a step S7 to check whether the rotation speed NI of the
input shaft 15 matches the product of the rotation speed NO of the
output shaft 16 and the current gear ratio G of the automatic
transmission 14.
When the input shaft rotation speed sensor condition judging device
18 and the output shaft rotation sensor condition judging device 21
judge that the rotation speed NI of the input shaft 15 matches the
product of the rotation speed NO of the output shaft 16 and the
current gear ratio G of the automatic transmission 14 at the step
S7, the fail-safe process of the input shaft rotation speed sensor
fail-safe processing device 26 and/or the output shaft rotation
speed sensor fail-safe processing device 29 is terminated since the
detection signals of the input shaft rotation speed sensor 19 and
the output shaft rotation speed sensor 20 are in normal state at a
step S8. On the other hand, when the rotation speed NI of the input
shaft 15 does not match the product of the rotation speed NO of the
output shaft 16 and the current gear ratio G of the automatic
transmission 14 as checked at the step S7, the process directly
goes END.
It should be noted that the judgement conditions for the normal
state and faulty state of the input and output shaft rotation speed
sensors 19 and 21 should not be specified to the shown conditions,
but can be selected in various ways depending upon necessity or so
forth.
Although the invention has been illustrated and described with
respect to an exemplary embodiment thereof, it should be understood
by those skilled in the art that the foregoing and various other
changes, omissions and additions may be made therein and thereto,
without departing from the spirit and scope of the present
invention. Therefore, the present invention should not be
understood as limited to the specific embodiment set out above but
to include all possible embodiments which can be embodied within a
scope encompassed and equivalents thereof with respect to the
features set out in the appended claims.
* * * * *